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^ SHORT METHODS -^ 

HG 1628 

. G62 ~~ *"°'' 

1884 

Copy 1 COMPUTING 

INTEREST AND DISCOUNT. 



100 DATS IN.EREST RULE. 



HENRY GOLDMAN])?; 

Author of the '■'■Electric Detector,'''' Etc. 
New York. 

1884. 



Copyright, 1884, by HENRY GOLDMANN . 
All Rights Reserved. 



CLAYTON St SON, PRS , 314 UOCUST. ST. LOUIS. 




^i INTEREST 

\ 

Is the money paid for the use of money ; 
Principal, the money on which interest is 
paid ; Rate of Interest, the number of 
per cent., and Amount, the principal plus the 
interest. 

To find the interest if the time is given in days. 

100 DAYS INTEREST RULE. 



1. Divide the principal by one of the key num- 
bers of the following table, according to the rate. 

2. Add to or subtract from the result the part 
which the corresponding column indicates. 

The answer is the interest of the given principal 
at the given rate for 1, 10 or 100 days, according to 
how many places to the left the decimal point is re 
moved. 1 place for 100 days, 2 places for 10 days, 
3 places for 1 day. To obtain the interest for 
any given number of days, multiply the hundreds, 
tens or units of days by the corresponding amount 
of interest and add the products together. 

Note. — The key numbers for the most frequent rates can he 
easily kept in mind. The parts have to be taken of the resuli 
of the division by the key number, and not of the principal, 
Where no part is indicated, the division by the key number is 
sufficient. 



To find the inierest if the time is given in years: 

Multiply the principal by the product of the num- 
ber of years and the rate, and remove the decimal 
point two places to the left. 

EXAMPLE. 

$630 at 8% for 3 years. 

8X3=24 630 

24 • 



Answer, $151.20 
To find the interest for 1 year^ multiply the prin- 
cipal by the rate, and remove the decimal point two 
places to the left. 

To find the principal : 

1. If the time is given in days^ multiply the in- 
terest by 36, divide by the product of the number of 
days and the rate and remove the decimal point three 
places to the right. 

2. If the time is give7t i7t months^ multiply the 
interest by 12, divide by the product of the number 
of months and the rate and remove the decimal 
point two places to the right. 

3. If the time is give7i in year s^ divide the inter- 
est by the product of the number of years and the 
rate, and rem.ove the decimal point two places to 
the right. 

To find the rate: 

Apply the rules given for finding the principal, 
substituting the principal for the rate. 

To find the time : 

1. /;/ days^ multiply the interest by 36, divide by 
the product of the principal and the rate, and re- 
move the decimal point three places to the right. 

2. I?t months^ multiply the interest by 12, divide 
by the product of the principal and the rate, and 
remove the decimal point two places to the right. 

3. In years, divide the interest by the product of 
the principal and the rate, and remove the decimal 
point two places to the right. 




^ INTSRSST i^ 

Is the money paid for the use of money ; 
Principal, the money on which interest is 
paid ; Rate of Interest, the number of 
per cent., and Amount, the principal plus the 
interest. 

To find ihe interest if the time is given in days. 

100 DAYS INTEREST RULE. 



1. Divide the principal by one of the key num- 
bers of the following table, according to the rate. 

2. Add to or subtract from the result the part 
which the corresponding column indicates. 

The answer is the interest of the given principal 
at the given rate for 1, 10 or 100 days, according to 
how many places to the left the decimal point is re 
moved. 1 place for 100 days, 2 places for 10 days, 
3 places for 1 day. To obtain the interest foi 
anv given number of days, multiply the hundreds, 
tens or units of days by the corresponding amount 
of interest and add the products together. 

Note. — The key numbers for the most frequent rates can he 
easily kept in mind. The parts have to be taken of the resul 
of the division by the key number, and not of the principal 
Where no part is indicated, the division by the key number h 
sufficient. 






Is the money paid for the use of mone)- ; 
Principai., the money on which interest is 
paid ; Ratk of Interest, the number of 
per cent., and Amount, the principal plus the 

To find the interest if the time is given in days. 

100 DAYS INTEREST RULE. 

1. Divide the principal by one of the l<ey num- 
bers of the following table, according to the rate. 

2. Add to or subtract from the result the part 
which the corresponding column indicates. 

The answer is the interest of the given principal 
at the given rate for 1, 10 or 100 days, according to 
how many places to the left the decimal point is re- 
moved. 1 place for 100 days, 2 places for 10 days, 
3 places for 1 day. To obtain the interest for 



lumber of days, multiply tl 
ts of days by the corresponc 



lundreds, 



RATE. 


Key Number 


PART 


Percent. 


Divide by 


to be added 


to be deducted. 


3 
34 


IS 
12 


One 


sixth 






f 

34 


S 






One 
One-t 


vemti 


I 


6 
4 


One- 
One 


welfth, 
sixth. 

third. ' 






10 
^2 








One- 
One-t 


welftii 



EXAMPLE. 

$136.43 at 5% for 113 days. 

6)136.43 Interest for 100 days, 1.805... |1. Ill 

^273 " " 10 " O.ISH... 1! 

- I 3.78 " " Ji " 0.056... _J 

18.95 Interest for 113 da^ys = .$2.1; 



Short Interest Rule. 



EXAMPLE. 
$3G5.44 at G% for 54 days. 



$3.28 6% for 54 day 



The "100 Days Interest Rule" permits a 
general application, while the "Short Inter- 
est Rule" will be found practical in a num- 
ber of special cases'. Both rules combined 
give an interest method, which has no equal. 
To find the interest for several items at once : 
Multiply each item* by the given number of days, 

of the following key numbers, according to"the'^n?te! 



... 360 



, . 60 



To find the interest if the time is given in months : 



Multiply 



th( 






Dnths by 30 



iponding number of daysf and appiv th 
100 Days'' or the "Short Interest Rule." 
EXAMPLE. 
$12.T at 7% for 3 months and 12 days. 
6)125.00, 3X30+12=102 days. 

" for 100 days=$2.43 



+ i 3.47, 
24.30, 



t for 102 days=$2.4! 






To find the interest if the time is given in years: 



EXAMPLE. 

$()30 at 8% for 3 years. 

8X3=24 630 



To find the principal : 

fewest bC3t diWde'bfMhe irot.ct oT" "''''' ^ 
pbcVsto the rfght" '*^'"'""' ^cccuna po.nt 



To fmd the rate : 




Apply the rules given f 


.^■r™^'' 


To find the time : 




1. /« rfffj-s, multiply the 
the product of the princip 

bv the product of lb. ,., 
remove the decimal pcnn 
3. I„ years, divide tin , 


'."']";!,"''',■', 


the principal and the rate, 


ukI rL-m.ne 



•^ DISCOUNT ■<- 

Is an allowance for the payment of money 
before it becomes due. It must always be de- 
ducted from the face of a bill, note, etc., 
while interest is, as a rule, added to the given 
principal. 

Discount is figured at a certain rate, either with- 
out any given time, in which case one year is taken 
as the basis, or for a given number of days. The 
rules for computing interest find application in 
both cases. 

LIST DISCOUNT 

Is a deduction from the list price or the amount of 
a bill, customary in many branches of business. 

If 07ily a si7igle rate sJiould be deducted^ the net 
price or net amount is easily obtained by simply sub- 
tracting the rate from 100, multiplying the list price 
or the given amount by the difference, and remov- 
ing the decimal point of the product two places to 
the left. 

EXAMPLE. 

List price, $42.00; list discount, 15%. 
100 42 

— 15 85 

85 210 

336 



Answer, $35.70 Net price. 

If several rates should be deducted successively 
subtract eti^ch of the given rates from 100, multiply 
the difftM-ences, and place the decimal point in fron 
of the product. The list price or the amount o 
bill multiplied by this product gives the desired ne 
price or net amount. 



EXAMPLE. 

Amount of bill, according to list prices, $^25.00 
List discount, 40%, 20% and 5%. 

100 100 100 

_ 40 — 20 — 5 

60* X 80* X 95 ::= 450,000* 
425 
.156 



2550 
2125 Answer, $193.80 Net amount. 

1700 



193.800 

PROFIT AND LOSS. 

Some important questions, frequently occuring 
in business, find their practical solution in the fol- 
lowing lines : 

To ascertain the rate of the profit or hss, if the 
buying price is taken as basis : 

Multiply the difference between the buying and 
the selling price by 100, and divide the product by 
the given buying price. f 

To ascertain the rate of the profit or loss, if the 
selling price is taken as basis : 

Multiply the difterence between the buying and 
the selling price by 100, and divide the product by 
the given selling price. f 

^Ciphers in the lowest places don't need to be considered. 

flf the selling price is larger than the buying price, the ans- 
wer is a profit. If the buying- price is larger than the selling 
price, the answer is a loss. 



^ DISCOUNT ■<• EXAMPLE. 
Pi-Hicipni. go* -^ HO* X 03 = 450,000* 

ipgsSi5= 1 ., 

LIST DISCOUNT ^^^ 

a bl.^c:^n;;:;Mnill'^,^nch Nonbusiness.' "' PROFIT AND LOSS. 

fiiiiiiii =£;?=—-•='= 

i:\ .\M I'Li:. 6(////J^ /ir/ce is taken as basis : 

List pi-icc, $ iL'.dll ; lisl .lisanint, 15%. thelelHn'i '!'L'hvTwr'^,n'd''divide 't^e ''"od"m-r'b'' 


LIBRARY OF CONGRESS % 

iiiiriiiiii'iii:|iiiii:iii[iii[ 

To gam on t/,e buyin (^ 021 062 037 

.■> *, miiltiiay lie same uv :^., am wm iub diuiiuui oy ^" 

10 " " " 11, " •■ 10 
124 " " " u! " •■ 8 
15 u ., ,. 2:!, " " 20 
20 " " " 12, " " 10 

30 '. .. .. 18,' ." " 10 
33J " '^' " 4, " " 3 

Vo " " " 14', " " 10 
4-, ,. « u 29, " " 20 
.Ml " '■ " 1.5, " " 10 

'■'•■■ !! ii !! ■"-' !! ", "•? 

7I>' 17,' " " lb 

SI) " •' •' IS, '■ " 10 
!)ll " " " 19, " " 10 

To gain on Me selling price : 

5 'A , miiitiply tie Mylia price Dy 20, ami divide lie proilict liy 1 

!i.:; :: :: ^^; :: :: ? 
1:; :: :; ? ;; :: 1 

hn" ■' " -i, " "2 

:i5 " '■ " 20, " " 13 

HI 1' II II 10, II II 

';,';»;! .. .. lb; .< .1 I 

so ■' II 11 10, |- ." 2 


-> SHORT METHODS <- 

HG 1628 

.G62 """'^-- 

1884 

Copy 1 COMPUTING 

INTEREST AND DISCOUNT. 


100 DATS INiEREST RULE. 

HENRY GOLDMANN, 

A,Mor of the ^'Electric Detector:' Etc. 

New Yokn. 

1SS4. 


Coi'ViuGHT, 1SS4, BY HENRY GOLDMAN K. 
All Kights Reserved. 


— ---— 



EXAMPLE. 

Amount of bill, according to list prices, $^25.00 
List discount, 40%, 20% and 5%. 

100 100 100 

— 40 — 20 — '^ 

60* X 80* X 95 .= 450,000* 
425 
.456 



2550 
2125 Answer, $193.80 Net amount. 

1700 



193.800 

PROFIT AND LOSS. 

Some important questions, frequently occuring 
I business, find their practical solution in the tol- 
wing lines : 

ascertain the rate of the profit or ioss, if the 
buying price is taken as basis : 

Multipl}^ the difference between the buying and 
e selling price by 100, and divide the product by 
e given buying price. f 

ascertain the rate of the profit or toss, if the 
selling price is taken as basis : 

Multiply the difference between the buying and 
e selling price hy 100, and divide the product by 
e given selling price. f 

'^Ciphers in the lowest places don't need to be considered, 
flf the selling price is larger than the buying price, the ans- 
tx is a profit. If the buying price is larger than the selling 
ice, the ans^ver is a loss. 



LIBRARY OF CONGRESS 

To ffa,n an the buyin ^ 021 062 037 



10 
12i 
15 
20 
25 
30 
33i 
35 

40 ' 
4^ ' 
50 ' 
60 ' 
661 * 
70 ' 
80 ' 
90 ' 



%, multiply tlie same uy 21, auu uivmc mu diuuuui uy -2u 



n, 

9, 
2^ 
12, 

•>> 

13, 
4, 

27, 

14, 

29, 
15, 

16, 

17, 

18, 
19, 



10 

8 
20 
10 

4 
10 

3 
20 
10 
•20 
10 
10 

3 
10 
10 
10 



The profit on the buying price can reach any 
number of per cent. 

To gain on ihe selling price : 

5 % , ffluitipiy me Duylng price liy 20, and divide the product Dy 1 9 
10 '' " <^ ^~ 

124'* u u 

15 '* " " 

25 '^ '* *' 

30 '' " 

334'* *' " 

35 " *' 

40 *' *' " 

45 " " " 

50 " ** " 

60 ** ** 

66|" ** ** 

70 *' *' ** 

80 "- " *' 

90 '* " '' 

The profit on the selling price can never reach 
100%, for in this case the buying price is reduced to 
nothing. 



10, 




9 


s, 




7 


20, 




17 


10, 




' 8 


4, 




3 


10, 




' 7 


3, 




2 


20, 




13 


10, 




6 


20, 




11 


2, 




1 


10,' 




' 4 


3, 




1 


10, 




3 


10, 




' 2 


10, 




1 



\ 



